Lynn Margulis (born Lynn Petra Alexander;[1][2] March 5, 1938 – November 22, 2011)[3] was an American evolutionary theorist, science author, educator, and popularizer, and was the primary modern proponent for the significance of symbiosis in evolution. Historian Jan Sapp has said that "Lynn Margulis’s name is as synonymous with symbiosis as Charles Darwin's is with evolution."[4] In particular, Margulis transformed and fundamentally framed current understanding of the evolution of cells with nuclei – an event Ernst Mayr called "perhaps the most important and dramatic event in the history of life"[5] – by proposing it to have been the result of symbiotic mergers of bacteria. Margulis was also the co-developer of the Gaia hypothesis with the British chemist James Lovelock, proposing that the Earth functions as a single self-regulating system, and was the principal defender and promulgator of the five kingdom classification of Robert Whittaker.

Throughout her career, Margulis’ work could arouse intense objection (one grant application elicited the response, "Your research is crap, do not bother to apply again"[4]), and her formative paper, "On the Origin of Mitosing Cells," appeared in 1967 after being rejected by about fifteen journals. Still a junior faculty at Boston University at the time, her theory that cell organelles such as mitochondria and chloroplasts were once independent bacteria was largely ignored for another decade, becoming widely accepted only after it was powerfully substantiated through genetic evidence. Margulis was elected a member of the US National Academy of Sciences in 1983. President Bill Clinton presented her the National Medal of Science in 1999. The Linnean Society of London awarded her the Darwin-Wallace Medal in 2008.

Called "Science's Unruly Earth Mother",[6] a "vindicated heretic",[7] or a scientific "rebel",[8] Margulis was a strong critic of neo-Darwinism.[9] Her position sparked lifelong debate with leading neo-Darwinian biologists, including Richard Dawkins,[10]George C. Williams, and John Maynard Smith.[4]:30, 67, 74–78, 88–92 Margulis' work on symbiosis and her endosymbiotic theory had important predecessors, going back to the mid-19th century – notably Konstantin Mereschkowski, Boris Kozo-Polyansky (ru) (1890-1957), and Ivan Wallin – and Margulis took the unusual step of not only trying to promote greater recognition for their contributions, but of personally overseeing the first English translation of Kozo-Polyansky's Symbiogenesis: A New Principle of Evolution, which appeared the year before her death. Many of her major works, particularly those intended for a general readership, were collaboratively written with her son Dorion Sagan.

Lynn Margulis was born in Chicago, to a Jewish, Zionist family.[11] Her parents were Morris Alexander and Leona Wise Alexander. She was the eldest of four daughters. Her father was an attorney who also ran a company that made road paints. Her mother operated a travel agency.[12] She entered the Hyde Park Academy High School in 1952,[13] describing herself as a bad student who frequently had to stand in the corner.[2]

A precocious child, she was accepted at the University of Chicago Laboratory Schools[14] at the age of fifteen:[15][16][17] In 1957, at age 19, she earned a BA from the University of Chicago in Liberal Arts, and then completed a master's degree at the University of Chicago in genetics and zoology at age 22. She joined the University of Wisconsin to study biology under Hans Ris and Walter Plaut, her supervisor, and graduated in 1960 with an MS in genetics and zoology. (Her first publication was with Plaut, on the genetics of Euglena, published in 1958 in the Journal of Protozoology.)[18] She then pursued research at the University of California, Berkeley, under the zoologist Max Alfert. Before she could complete her dissertation, she was offered research associateship and then lecturership at Brandeis University in Massachusetts in 1964. It was while working there that she obtained her PhD from the University of California, Berkeley in 1965. Her thesis was An Unusual Pattern of Thymidine Incorporation in Euglena.[19] In 1966 she moved to Boston University, where she taught biology for twenty-two years. She was initially an Adjunct Assistant Professor, and appointed to Assistant Professor in 1967. She was promoted to Associate Professor in 1971, to full Professor in 1977, and to University Professor in 1986. In 1988 she was appointed Distinguished Professor of Botany at the University of Massachusetts at Amherst. She was Distinguished Professor of Biology in 1993. In 1997 she transferred to the Department of Geosciences at Amherst to become Distinguished Professor of Geosciences "with great delight",[20] the post which she held until her death.[21]

Margulis married astronomer Carl Sagan in 1957 soon after she got her bachelor's degree. Sagan was then a graduate student in physics at the University of Chicago. Their marriage ended in 1964, just before she completed her PhD. They had two sons, Dorion Sagan, who later became a popular science writer and her collaborator, and Jeremy Sagan, software developer and founder of Sagan Technology. In 1967, she married Thomas N. Margulis, a crystallographer. They had a son Zachary Margulis-Ohnuma, New York City criminal defense lawyer, and a daughter Jennifer Margulis, teacher and author.[22][23] They divorced in 1980. She commented, "I quit my job as a wife twice," and, "it’s not humanly possible to be a good wife, a good mother and a first-class scientist. No one can do it—something has to go."[23] In the 2000s she had a relationship with fellow biologist Ricardo Guerrero.[13] Her sister Joan Alexander married Nobel Laureate Sheldon Lee Glashow; another sister, Sharon, married mathematician Daniel Kleitman.

She was an agnostic,[13] and a staunch evolutionist. But she totally rejected the modern evolutionary synthesis,[9] and said: "I remember waking up one day with an epiphanous revelation: I am not a neo-Darwinist! It recalled an earlier experience, when I realized that I wasn't a humanistic Jew. Although I greatly admire Darwin's contributions and agree with most of his theoretical analysis and I am a Darwinist, I am not a neo-Darwinist.[24] She argued that "Natural selection eliminates and maybe maintains, but it doesn't create", and maintained that symbiosis was the major driver of evolutionary change.[9]

In 1966, as a young faculty member at Boston University, Margulis wrote a theoretical paper titled "On the Origin of Mitosing Cells".[28] The paper, however, was "rejected by about fifteen scientific journals," she recalled.[24] It was finally accepted by Journal of Theoretical Biology and is considered today a landmark in modern endosymbiotic theory. Weathering constant criticism of her ideas for decades, Margulis was famous for her tenacity in pushing her theory forward, despite the opposition she faced at the time.[2] The descent of mitochondria from bacteria and of chloroplasts from cyanobacteria was experimentally demonstrated in 1978 by Robert Schwartz and Margaret Dayhoff.[29] This formed the first experimental evidence for her theory.[2] The endosymbiosis theory of organogenesis became widely accepted in the 1980s, when the genetic material of mitochondria and chloroplasts was found to be different from that of the symbiont's nuclear DNA.[30]

In 1995, English evolutionary biologist Richard Dawkins had this to say about Lynn Margulis and her work:

I greatly admire Lynn Margulis's sheer courage and stamina in sticking by the endosymbiosis theory, and carrying it through from being an unorthodoxy to an orthodoxy. I'm referring to the theory that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells. This is one of the great achievements of twentieth-century evolutionary biology, and I greatly admire her for it.[24]

Margulis later formulated a theory to explain how symbiotic relationships between organisms of often different phyla or kingdoms are the driving force of evolution and genetic variation is proposed to occur mainly as a result of transfer of nuclear information between bacterial cells or viruses and eukaryotic cells.[6] While her organelle genesis ideas are widely accepted, symbiotic relationships as a current method of introducing genetic variation is something of a fringe idea.[6]

She also held a negative view of certain interpretations of Neo-Darwinism that she felt were excessively focused on inter-organismic competition, as she believed that history will ultimately judge them as comprising "a minor twentieth-century religious sect within the sprawling religious persuasion of Anglo-Saxon Biology."[6] She also believed that proponents of the standard theory "wallow in their zoological, capitalistic, competitive, cost-benefit interpretation of Darwin – having mistaken him... Neo-Darwinism, which insists on [the slow accrual of mutations by gene-level natural selection], is in a complete funk."[6]

She opposed competition-oriented views of evolution, stressing the importance of symbiotic or cooperative relationships between species.[6]

Margulis initially sought out the advice of Lovelock for her own research: she explained that, "In the early seventies, I was trying to align bacteria by their metabolic pathways. I noticed that all kinds of bacteria produced gases. Oxygen, hydrogen sulfide, carbon dioxide, nitrogen, ammonia — more than thirty different gases are given off by the bacteria whose evolutionary history I was keen to reconstruct. Why did every scientist I asked believe that atmospheric oxygen was a biological product but the other atmospheric gases — nitrogen, methane, sulfur, and so on — were not? 'Go talk to Lovelock,' at least four different scientists suggested. Lovelock believed that the gases in the atmosphere were biological."[24]

Margulis met with Lovelock, who explained his Gaia hypothesis to her, and very soon they began an intense collaborative effort on the concept.[24] One of the earliest significant publications on Gaia was a 1974 paper co-authored by Lovelock and Margulis, which succinctly defined the hypothesis as follows: "The notion of the biosphere as an active adaptive control system able to maintain the Earth in homeostasis we are calling the ‘Gaia hypothesis.’"[31]

Like other early presentations of Lovelock’s idea, the Lovelock-Margulis 1974 paper seemed to give living organisms complete agency in creating planetary self-regulation, whereas later, as the idea matured, this planetary-scale self-regulation was recognized as an emergent property of the Earth system, life and its physical environment taken together (Lovelock, 1988).[32] When climatologist Stephen Schneider convened the 1989 American Geophysical Union Chapman Conference around the issue of Gaia, the idea of “strong Gaia” and “weak Gaia” was introduced by James Kirchner, after which Margulis was sometimes associated with the idea of “weak Gaia,” incorrectly (her essay "Gaia is a Tough Bitch" dates from 1995 – and it stated her own distinction from Lovelock as she saw it, which was primarily that she did not like the metaphor of Earth as a single organism, because, she said, "No organism eats its own waste"[24]). In her 1998 book Symbiotic Planet, Margulis explored the relationship between Gaia and her work on symbiosis.[33]

The entire life on earth was traditionally classified into five kingdoms, as introduced by Robert Whittaker in 1969.[34] Margulis became the most important supporter, as well as critic[35] – in the sense that she was the first to recognize the limitations of Whittaker's classification of microbes.[36] But later discoveries of new organisms, such as archaea, and emergence of molecular taxonomy challenged the concept.[37] By the mid-2000s, most scientists began to agree that there are more than five kingdoms.[38][39] Margulis became the most important defender of the five kingdom classification. She rejected the three-domain system introduced by Carl Woese in 1990, which gained wide acceptance. She introduced an modified classification by which all life forms, including the newly discovered, could be integrated into the classical five kingdoms. According to her the main problem, archaea, falls under the kingdom Prokaryotae alongside bacteria (in contrast to the three-domain system which treat archaea as a higher taxon than kingdom, or the six-kingdom system which holds that it is a separate kingdom).[37] Her concept is given in detail in her book Five Kingdoms, written with Karlene V. Schwartz.[40] It is mainly because of her that this five-kingdom system survives.[20]

It has been suggested that initial rejection of Margulis’ work on the endosymbiotic theory, and the controversial nature of it as well as Gaia theory, made her identify throughout her career with scientific mavericks, outsiders and unaccepted theories generally.[4] In the last decade of her life, while key components of her life’s work began to be understood as fundamental to a modern scientific viewpoint – the widespread adoption of Earth System Science and the incorporation of key parts of endosymbiotic theory into biology curricula worldwide – Margulis if anything became more embroiled in controversy, not less. Journalist John Wilson explained this by saying that Lynn Margulis “defined herself by oppositional science,”[41] and in the commemorative collection of essays Lynn Margulis: The Life and Legacy of a Scientific Rebel, commentators again and again depict her as a modern embodiment of the "scientific rebel",[4] akin to Freeman Dyson’s 1995 essay, The Scientist as Rebel, a tradition Dyson saw embodied in Benjamin Franklin, and which he believed to be essential to good science.[42] At times, Margulis could make highly provocative comments in interviews that appeared to support her most strident critics’ condemnation. The following describes two of these controversies.

In 2009, via a then-standard publication-process known as "communicated submission" (which bypassed traditional peer review), she was instrumental in getting the Proceedings of the National Academy of Sciences (PNAS) to publish a paper by Donald I. Williamson rejecting "the Darwinian assumption that larvae and their adults evolved from a single common ancestor."[43][44] Williamson's paper provoked immediate response from the scientific community, including a countering paper in PNAS.[43] Conrad Labandeira of the Smithsonian National Museum of Natural History said, "If I was reviewing [Williamson's paper] I would probably opt to reject it," he says, "but I'm not saying it's a bad thing that this is published. What it may do is broaden the discussion on how metamorphosis works and...[on]...the origin of these very radical life cycles." But Duke University insect developmental biologist Fred Nijhout said that the paper was better suited for the "National Enquirer than the National Academy."[45] In September it was announced that PNAS would eliminate communicated submissions in July 2010. PNAS stated that the decision had nothing to do with the Williamson controversy.[44]

In 2009 Margulis and seven others authored a position paper concerning research on the viability of round body forms of some spirochetes, "Syphilis, Lyme disease & AIDS: Resurgence of 'the great imitator'?",[46] which states that, "Detailed research that correlates life histories of symbiotic spirochetes to changes in the immune system of associated vertebrates is sorely needed," and urging the "reinvestigation of the natural history of mammalian, tick-borne, and venereal transmission of spirochetes in relation to impairment of the human immune system." The paper did not question the existence of HIV or AIDS, nor that HIV causes AIDS, but suggested that syphilis could have been a co-factor in the spread of AIDS. In a Discover Magazine interview with Dick Teresi published less than six months before her death, however, Margulis spoke provocatively of how, "the set of symptoms, or syndrome, presented by syphilitics overlaps completely with another syndrome: AIDS," and also noted that "Kary Mullis [winner of the 1993 Nobel Prize for DNA sequencing, and well known for his unconventional scientific views] said in an interview that he went looking for a reference substantiating that HIV causes AIDS and discovered, 'There is no such document.' "[9] This elicited widespread suggestions that Margulis was an "AIDS denialist", with Jerry Coyne notably writing on his Why Evolution is True blog about Margulis' supposed "notion that AIDS is really syphilis, not viral in origin at all."[1]Seth Kalichman, a social psychologist who studies behavioral and social aspects of AIDS, cited her 2009 paper as an example of AIDS denialism "flourishing",[47] and asserted that her "endorsement of HIV/AIDS denialism defies understanding."[48] In the Discover Magazine interview, Margulis discussed with Teresi the primary grounds for her initial interest in the material of the 2009 "AIDS" paper, being that "I’m interested in spirochetes only because of our ancestry. I’m not interested in the diseases," and stated that to her the fact that both Treponema (the spirochete which causes syphilis) and Borrelia (the spirochete which causes Lyme disease) only have retained about 20% of the genes they need to live freely outside of their human hosts, they should be considered as symbionts.[9]

Margulis argued that the September 11 attacks were a "false-flag operation, which has been used to justify the wars in Afghanistan and Iraq as well as unprecedented assaults on ... civil liberties." She claimed that there was "overwhelming evidence that the three buildings [of the World Trade Center] collapsed by controlled demolition."[4]